German Patent Application No. DE 44 20 282 describes a method and device for driving an electromagnetic consumer which includes a movable element. The consumer is a solenoid-operated valve for controlling the metering of fuel into an internal combustion engine. A switching instant when the movable element changes its position is determined within a timing window. This is achieved by analyzing the time characteristic of a variable that corresponds to the current flowing through the consumer. During the timing window in which the current is analyzed, the voltage being applied to the consumer is controlled to a constant value in closed loop or open loop.
In the cold start-up phase, the leads to the consumer are low-resistance, so that under constant voltage conditions, the currents reach a higher level than in normal operation. If provision is made for a current monitoring to switch off the output stage as of a specific threshold value, this can lead to the output stage being switched off by the current monitoring.
In addition, clear differences are apparent in the resistance of the individual current leads to the individual consumers. Therefore, if the voltage within the timing window is preset to be so low that, under the most unfavorable conditions, the result is that the output stage is not switched off, this can lead, in turn, to such a small current flowing through the consumer during the timing window that the forces acting upon the movable element are not significant enough to retain the element in its position. When working with a solenoid-operated valve, this can lead to a short-term re-opening or re-closing.